Environmental activist Erin Brockovich has corrected misinformation regarding her investigation into the medical mystery in an upstate New York town where a group of teenagers has displayed symptoms similar to Tourette syndrome, saying that her research is still preliminary.

Nearly two dozen people, including one 36-year-old, in the upstate New York village of LeRoy are now experiencing uncontrollable tics, seizures and outbursts they might have been caused by a chemical spill in the town more than 40 years ago.

In a statement released Tuesday, Brockovich said she is still investigating a plume from a 1970 train derailment in LeRoy, which dumped cyanide and trichloroethylene (TCE) -- a chlorinated hydrocarbon used to de-grease metal parts -- within three miles of the village's high school.

The Environmental Protection Agency says that TCE can affect the central nervous system, and cause dizziness, headache, sleepiness, nausea, confusion, blurred vision and facial numbness. It is suspected of being inked to the symptoms among LeRoy's local teens.

Brockovich associate Bob Bowcock reportedly said Feb. 11 that samples were taken from the wells of private residences had not migrated west and south -- toward LeRoy High School -- as some had feared. Although at the time Browcock said that the investigation would continue for the next several months, Brockovich Tuesday said that the tests he referred to were preliminary.

"Contrary to an erroneous news report, I want to make clear that my investigation into possible sources of environmental contamination in LeRoy, New York that may or may not be linked to the serious illnesses suffered by various members of the community is not complete," Brockovich said in a statement. "In fact, it appears the number of people in the area displaying alarming health issues that can be caused by TCE is growing.

"It took the EPA 40 years to investigate the contamination from the train derailment and it will take us more than 40 days to get to the root of the problem in LeRoy. I want to further stress that we have not ruled out the TCE plume from the train derailment as a source of contamination at LeRoy High School," she added.

Brockovich, 51, added that her team has many more areas of LeRoy to test, including the local quarry, six fracking wells at the high school and the Methyl tert-butyl ether (MtBE) contamination in local wells, while stressing that thoroughness is key in her investigation.

The original affected teenagers -- 14 girls and one boy -- all attended LeRoy Junior-Senior High School when they started showing symptoms last fall. Most of the teens have been diagnosed with conversion disorder, a psychological condition induced by stress that is sometimes called "mass hysteria" when occurring in clusters, such as in LeRoy.

Brockovich, who in 1996 famously linked a handful of cancer cases in California to contaminated drinking water, launched her investigation into the circumstances in LeRoy last month. The parents of those afflicted have since rallied behind her, demanding potential environmental causes behind the disease.

During a visit to the Le Roy High School property Jan. 28 to collect soil, air and water samples from the school grounds, Bowcock was asked by officials to leave.

Lana Clark, whose 16-year-old daughter, Lauren Scalzo, is another of the 15 students originally afflicted, sought help from a New Jersey neurologist who volunteered to come and see the girls. He offered an alternate theory: PANDAS, a diagnosis used to describe children who have a rapid onset of neurological conditions such as Tourette syndrome or obsessive compulsive disorder after a bacterial infection such as strep throat.

Doctors are not sure exactly how one causes the others, but some believe it is an autoimmune response. Clark said she trusts the PANDAS diagnosis and wants it investigated further.

"There's a great idea that what has brought on the PANDAs is an environmental issue and the school, they were saying, they did air quality testing within the school but it's like they almost have a refusal to go out and test the soil," Clark said. "We also know with the gas wells and the residue, there's a holding tank, maybe, and it's come out on the ground and killed neighboring trees and plants."

An investigation by the New York Department of Health found "no evidence of environmental or infection as the cause of the girls' illness," department spokesman Jeffrey Hammond said. "The school is served by a public water system. ... An environmental exposure would affect many people."

The possibility of an environmental trigger has been bolstered by reports of similar symptoms in two teens living in Corinth, a town 250 miles from LeRoy. The girls started showing symptoms in May, around the same time they passed through LeRoy on their way to a softball tournament in Ohio. At least one has since been diagnosed with Tourette syndrome.